Toxic metals may influence autism severity.

Dec 28, 2009

Adams, JB, M Baral, E Geis, J Mitchell, J Ingram, A Hensley, I Zappia, S Newmark, E Gehn, RA Rubin, K Mitchell, J Bradstreet, and JM El-Dahr. 2009. The severity of autism is associated with toxic metal body burden and red blood cell glutathioine levels. Journal of Toxicology doi:10.1155/2009/532640.


Children with higher levels of metals – such as lead and antimony – in their urine had more severe autism, suggesting that metal levels in their bodies may contribute to its seriousness.

The severity of a child's autism coincided with the levels of toxic metals excreted in their urine after treatment with a metals removal therapy, finds a study published in the Journal of Toxicology. The higher the levels of lead, antimony and other metals excreted, the more severe was the child's autism. The findings hold true across four independent tools used to assess autism severity.

The results suggest to researchers that these metals may contribute to the degree of autism symptoms in the children. Because these children had autism before the toxic metals were measured, the study does not address whether the metals cause autism or the sources of the metals.

Autism is a severe disorder that impacts social, communicative and behavioral function. It is increasingly diagnosed in young children and affects them for life. While widespread, its cause is not known.

Some researchers have noticed that autism symptoms are similar to symptoms associated with toxic metal poisoning. Because of this, mercury, lead and other metals have been scrutinized for possible links to autism. Yet, even though some human research evidence suggests a relationship between metals and autism, the exact relationship remains a mystery.

Sixty-three children aged 3 to 8 years old participated in the study. The children had no mercury dental fillings and were diagnosed with autism spectrum disorder. Researchers assessed the severity of autism using tools developed to either diagnose the condition or monitor the symptoms.

Measurements of toxic metals were taken from children’s urine before and after children were treated with oral dimercaptosuccinic acid (DMSA). DMSA is a medication approved for infant lead poisoning, though doctors sometimes use it to treat toxic exposure to other metals, like mercury. None of the children in the study had ever been treated with DMSA.

Lead and antimony excreted after the DMSA treatment were consistently associated with autism across the four severity assessment tools used. Mercury, aluminum and tin were associated with some – but not all – of the severity assessment tools. DMSA treatment significantly decreased urinary lead levels, as expected. This therapy also effectively removed a number of other toxic metals from the children, including tin, bismuth, tungsten, thallium, antimony and arsenic.

In these kinds of studies, the level of one type of metal found in a child is related to the level of another type of metal found in the same child. So even though the levels of lead and antimony in this study correlated to autism severity across all four of the assessment tools used, the researchers cannot be sure which of the individual metals measured relate to autism severity in this study. Identifying autism severity in people with only lead or antimony exposure might help to solve this question.

This study raises more questions about the role of toxic metal exposures in the severity of autism spectrum disorder. A larger study that assesses autism severity both before- and after- DMSA treatment, while documenting the effectiveness of DMSA treatment, would lend further credibility to the notion that toxic metals influence autism severity.

This study suggests that DMSA is effective therapy to remove a variety of toxic metals from children. Regulatory agencies could evaluate the treatment and develop appropriate treatment guidelines for DMSA uses.